CN114773665A

CN114773665A - Processing method for recycling polystyrene waste

Info

Publication number: CN114773665A
Application number: CN202210524437.XA
Authority: CN
Inventors: 罗兰·科泰
Original assignee: Polystyvert Inc
Current assignee: Polystyvert Inc
Priority date: 2014-10-03
Filing date: 2015-10-05
Publication date: 2022-07-22
Also published as: KR20220138014A; US20230002583A1; KR20240013289A; CA3147655A1; JP2017536469A; US20170298207A1; CA3042919A1; CA3042919C; KR102450016B1; WO2016049782A1; KR102314967B1; EP3575353A1; CN107001520B; CA2959082A1; CN110256727B; KR20210128029A; US11407878B2; ES2758521T3; US20220073696A1; EP3201246A1

Abstract

The invention relates to a processing method for recycling polystyrene waste. The invention also relates to the use of a combination of p-cymene and a non-solvent having a boiling point of 98 ℃ to 110 ℃ at a pressure of 1atm for the recovery of polystyrene and to a composition for the production of recovered polystyrene, said composition comprising polystyrene, p-cymene and a non-solvent having a boiling point of 98 ℃ to 110 ℃ at a pressure of 1 atm. The compositions and processing methods of the present invention allow for an increased life cycle of recycled polystyrene, yet they have a very low MFI, while avoiding the use of large amounts of additives and/or fillers.

Description

Processing method for recycling polystyrene waste

The application is a reissue application of Chinese patent application with application number 201910549840.6 entitled processing method for recycling polystyrene waste. The divisional application is a divisional application of a Chinese patent application having an original application number of 201580065085.4 and entitled processing method for recycling polystyrene waste.

Technical Field

The present disclosure relates to a process for recycling polystyrene waste. For example, it relates to a process for recycling polystyrene, which comprises dissolving polystyrene waste in a solvent such as p-cymene, followed by precipitation and washing of the polystyrene with a non-solvent.

Background

Polystyrene waste, for example, packaging for electronic products or furniture, food trays, goods and insulation can for example have an environmental impact.

For example, most polystyrene waste is buried in landfills, whether post-consumer or post-industrial. For example, more than 40,000 tons of polystyrene waste are buried annually in quebec. Further, 60,000 tons of new polystyrene are purchased and consumed annually in quebec.

Known processes for recycling polystyrene do not produce recycled polystyrene having the same properties as virgin polystyrene. For example, known processes for polystyrene do not produce recycled polystyrene having a Melt Flow Index (MFI) that meets the specifications for using recycled polystyrene for the same use as virgin polystyrene. To counteract this loss of mechanical properties, recycled polystyrene is blended with virgin polystyrene in proportions that can rarely exceed 20%, even for less stringent applications.

Most industrial polystyrene articles are not composed of polystyrene alone; for example, they may contain chemical species added to the polymer to modify some physical, biological, and/or chemical properties. Examples of additives are colorants, fillers, flame retardants, lubricants and plasticizers.

It would therefore be desirable to provide recycled polystyrene and a process for recycling polystyrene waste which would at least partially solve one of the mentioned problems, or would be an alternative to known processes for recycling polystyrene waste.

Disclosure of Invention

Thus, according to one aspect of the present disclosure, there is provided a recycled polystyrene having a melt flow index of less than about 25g/10min as measured according to ASTM D1238-13.

According to another aspect of the present disclosure, there is provided a recycled polystyrene having a melt flow index of less than about 25g/10min and an additive content of less than about 1 wt%, measured according to ASTM D1238-13.

According to another aspect of the present disclosure, there is provided a recycled polystyrene having a melt flow index of less than about 25g/10min as measured according to ASTM D1238-13 standard and an ash content of less than about 1 wt% as measured according to ASTM D5630-13 standard.

According to another aspect of the present disclosure, there is provided a recycled polystyrene having a melt flow index of less than about 25g/10min measured according to ASTM D1238-13 standard and an ash content of less than about 0.5 wt% measured according to ASTM D5630-13 standard.

According to another aspect of the present disclosure, there is provided recycled polystyrene having a melt flow index of less than about 25g/10 min.

According to another aspect of the present disclosure, there is provided a recycled polystyrene having a melt flow index of less than about 25g/10min as measured according to ASTM D1238-13.

According to another aspect of the present disclosure, there is provided a processing method of recycling polystyrene waste, including:

dissolving the polystyrene waste in p-cymene under conditions to obtain a polystyrene/p-cymene mixture;

adding a polystyrene/p-cymene mixture to a first portion of a hydrocarbon polystyrene non-solvent under conditions to obtain precipitated polystyrene and a first portion of a hydrocarbon waste stream;

separating the precipitated polystyrene from the first portion of the hydrocarbon waste stream;

optionally repeating dissolving, adding, and separating;

washing the precipitated polystyrene with a second portion of the hydrocarbon polystyrene non-solvent under conditions to obtain washed polystyrene and a second portion of the hydrocarbon waste stream;

separating the washed polystyrene from a second portion of the hydrocarbon waste stream;

washing the washed polystyrene with a third portion of hydrocarbon polystyrene non-solvent under conditions to obtain a second washed polystyrene and a third portion of hydrocarbon waste liquor;

separating the secondarily washed polystyrene from a third portion of the hydrocarbon waste stream; and

optionally drying the twice-washed polystyrene under conditions to obtain a dried polystyrene.

Thus, according to another aspect of the present disclosure, there is provided a process for recycling polystyrene waste, comprising:

optionally repeating dissolving, adding, and separating;

washing the washed polystyrene with a third portion of hydrocarbon polystyrene non-solvent under conditions to obtain a second washed polystyrene and a third portion of hydrocarbon waste;

separating the second washed polystyrene from a third portion of the hydrocarbon waste stream;

removing the remaining hydrocarbon waste liquid by wringing and/or compressing the secondarily washed polypropylene ethylene; and

the twice-washed polystyrene is dried under conditions to obtain a dried polystyrene.

The present disclosure also includes recycled polystyrene prepared according to the processing methods of recycled polystyrene waste of the present disclosure.

Polystyrene waste, such as expanded polystyrene waste, is typically bulky and light, whereas polystyrene/p-cymene mixtures typically have higher densities and can therefore be transported at less expense. Thus, if, for example, a polystyrene/p-cymene mixture is obtained at a first location, and the process further comprises transporting the polystyrene/p-cymene mixture to a second location where subsequent steps in the process are performed, then the process of the present disclosure can, for example, save on transportation costs.

The processing methods of recycled polystyrene waste of the present disclosure may, for example, allow for the removal of most additives (e.g., chemicals added to the polymer to modify some physical, biological, and/or chemical properties), and may produce recycled polystyrene with properties very close to those of virgin polystyrene. The recycled polystyrene produced by the processing methods of the present disclosure can be, for example, suitable for the same use as virgin polystyrene, such as for producing virgin polystyrene articles. For example, recycled polystyrene prepared by the processing methods of the present disclosure may have an MFI within an effective range, for example, for such uses.

It has been found that the recycled polystyrene of the present disclosure and the processing method to obtain said recycled polystyrene are quite useful. In fact, it was found that such recycled polymers and processing methods allow to provide recycled polystyrene with a very low content of additives (fillers and/or lubricants). This also results in the production of recycled polystyrene with a very low ash content. For example, when these processing methods are applied to white expanded or extruded polystyrene, the end product is very clear and transparent to light transmission. Such a feature of the polymers and processing methods of the present disclosure is very interesting because it allows to significantly increase the life cycle of the recycled polystyrene. In fact, the use of recycled polystyrene is generally quite limited in view of the various additives contained therein, and therefore they do not meet the requirements of certain uses and applications that can be carried out using polystyrene. Some manufacturers are also reluctant to use recycled polystyrene, since it has too high a content of additives and said additives may affect or reduce the properties of the polystyrene or of the products made with such recycled polystyrene. This is clearly not the case for the polymers and processing methods mentioned in this disclosure. Conversely, the very low amount of additives and/or fillers found in the polymers of the present disclosure allows the use of these recycled polystyrenes in many different applications and allows the recycling of these recycled polystyrenes several times, and the attainment of low MFI values, since the user of such products is not forced to recycle the products, and therefore high levels of additives and/or fillers are almost never obtained.

Thus, the polymers and processing methods of the present disclosure allow for an increased life cycle of recycled polystyrene (it is possible to recycle them multiple times while maintaining the desired specifications and properties), and they have a very low MFI while avoiding the use of large amounts of additives and/or fillers.

Drawings

In the following figures, various embodiments of the present disclosure are presented by way of example only:

fig. 1 is a schematic illustration of a processing method according to an embodiment of the present disclosure.

Detailed Description

Unless otherwise indicated, the definitions and embodiments described in this and other sections are intended to apply to all embodiments and aspects of the disclosure described herein, as understood by one of skill in the art, for which the definitions and embodiments described in this and other sections are appropriate.

As used in this disclosure, the singular forms "a", "an" and "the" include plural referents unless the content clearly dictates otherwise. For example, the inclusion of a "hydrocarbon polystyrene non-solvent" should be understood to mean one hydrocarbon polystyrene non-solvent, or some aspect of two or more additional hydrocarbon polystyrene non-solvents.

In embodiments comprising an "additional" or "second" component, such as an additional or second hydrocarbon polystyrene non-solvent, the second component as used herein is different from the other component or the first component. The "third" component is different from the other components, the first component and the second component, and similarly further enumerated or "additional" components are different.

The term "additive" as used herein refers to a chemical substance added to a polymer to modify at least one physical, biological, and/or chemical property. Non-limiting examples of additives are: colorants, fillers, flame retardants, lubricants, and plasticizers.

In understanding the scope of the present disclosure, the term "comprising" and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, "including", "having" and their derivatives. As used herein, the term "consisting of and derivatives thereof is intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but exclude the presence of other unstated features, elements, components, groups, integers, and/or steps. The term "consisting essentially of …" as used herein is intended to specify the presence of the stated features, elements, components, groups, integers, and/or steps, as well as features, elements, components, groups, integers, and/or steps, which do not materially affect the basic and novel characteristics of the stated features, elements, components, groups, integers, and/or steps.

Terms of degree such as "about" and "approximately" as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of at least + -5% or at least + -10% of the modified term if this deviation would not negate the meaning of the word it modifies.

The term "hydrocarbon polystyrene non-solvent" as used herein refers to, for example, a hydrocarbon based polystyreneIn a hydrocarbon compound or mixture thereof, wherein the polystyrene is substantially insoluble. The selection of an appropriate hydrocarbon polystyrene non-solvent for the processing methods of the present disclosure can be made by one skilled in the art. For example, one skilled in the art will appreciate that most of the non-polar additives (e.g., hexabromocyclododecane and silicone oil) and p-cymene typically found in polystyrene waste should be substantially soluble in hydrocarbon polystyrene non-solvents under the conditions used in the disclosed processing methods to obtain precipitated polystyrene and in the steps that include washing with hydrocarbon polystyrene non-solvents. It will also be understood by those skilled in the art, for example, to select a material having a glass transition temperature (T) about or slightly above that of the polystyrene waste to be recycled_g) Hydrocarbon polystyrene non-solvents of boiling point of (a) are useful.

The examples provided below are non-limiting and serve to better exemplify the processing methods of the present disclosure.

An exemplary process flow diagram of the processing method of the present disclosure is shown in fig. 1. Exemplary process 10 is a process for recycling polystyrene waste. Referring to fig. 1, in an exemplary processing method 10, polystyrene waste may be dissolved 12 in p-cymene under conditions to obtain a polystyrene/p-cymene mixture. For example, if the polystyrene/p-cymene mixture includes insoluble material, the polystyrene/p-cymene mixture can optionally be filtered 14 under conditions to remove the insoluble material. The polystyrene/p-cymene mixture can then be added 16 to the first portion of the hydrocarbon waste stream under conditions to obtain precipitated polystyrene and the first portion of the hydrocarbon waste stream. Next, the precipitated polystyrene may be separated from the first portion of the hydrocarbon waste stream. The precipitated polystyrene may then be washed 18 with a second portion of the hydrocarbon polystyrene non-solvent under conditions to obtain washed polystyrene and a second portion of the hydrocarbon waste stream. The washed polystyrene may then be separated from the second portion of the hydrocarbon waste stream. The washed polystyrene can then be washed 20 with a third portion of the hydrocarbon polystyrene non-solvent under conditions to obtain a second washed polystyrene and a third portion of the hydrocarbon waste stream. The second washed polystyrene can be separated from the third portion of the hydrocarbon waste liquid. The remaining hydrocarbon waste liquid may optionally be removed by wringing and/or compressing the twice-washed polystyrene. The twice washed polystyrene may then be optionally dried 22 under conditions to obtain a dried polystyrene. The dried polystyrene may then optionally be packaged 24, for example, the processing method may further include treating the dried polystyrene under conditions to obtain polystyrene particles, and the polystyrene particles may be packaged 24. The p-cymene and/or hydrocarbon polystyrene non-solvent can optionally be recovered 26, for example by a process comprising distilling a first portion of a hydrocarbon waste stream, a second portion of a hydrocarbon waste stream, and/or a third portion of a hydrocarbon waste stream under conditions to obtain the p-cymene and/or hydrocarbon polystyrene non-solvent. P-cymene can optionally be recovered for solubilization 12. The hydrocarbon polystyrene non-solvent may optionally be recovered for addition 16, first wash 18, and/or second wash 20.

For example, the polystyrene/p-cymene mixture can comprise polystyrene in an amount equal to or less than about 33 wt%, based on the total weight of the polystyrene/p-cymene mixture.

For example, the polystyrene/p-cymene mixture can comprise polystyrene in an amount of about 10 wt% to about 30 wt%, based on the total weight of the polystyrene/p-cymene mixture.

For example, the polystyrene/p-cymene mixture can comprise polystyrene in an amount of about 14 wt% to about 28 wt%, based on the total weight of the polystyrene/p-cymene mixture.

For example, the polystyrene/p-cymene mixture can comprise polystyrene in an amount of about 15 wt% to about 27 wt%, based on the total weight of the polystyrene/p-cymene mixture.

For example, the polystyrene/p-cymene mixture can comprise polystyrene in an amount of about 16 wt% to about 25 wt%, based on the total weight of the polystyrene/p-cymene mixture.

For example, the polystyrene waste may be dissolved in p-cymene in a container having a chamber containing p-cymene and at least one opening toward the chamber for adding the polystyrene waste to the p-cymene, and the processing method may further include adding the polystyrene waste to the p-cymene contained within the chamber.

For example, the container may further comprise an outlet.

For example, the container may further comprise means for driving polystyrene waste into p-cymene.

For example, the means for driving polystyrene waste into p-cymene may comprise a metal mesh inside the container.

For example, the container may further comprise means to indicate when the volume of the chamber has been reached.

For example, the means to indicate when the volume of the chamber is reached may be an indicator light.

For example, the indicator light may be connected to a float switch in the room.

For example, the polystyrene/p-cymene mixture can comprise insoluble material, and the method can further comprise filtering the polystyrene/p-cymene mixture under conditions to remove insoluble material prior to adding the polystyrene/p-cymene mixture to the first portion of the hydrocarbon polystyrene non-solvent. For example, the insoluble material may be selected from the group consisting of polystyrene/butadiene mixtures, styrene copolymer dust, adhesives, metals, wood, plastics, contaminants, and mixtures thereof. For example, the filtering may include multiple stages of filtering from coarse to fine. For example, butadiene is soluble in p-cymene unless it has been heavily crosslinked.

For example, the conditions to obtain precipitated polystyrene and the first portion of the hydrocarbon waste liquid may comprise adding a polystyrene/p-cymene mixture to the first portion of the hydrocarbon polystyrene non-solvent at the boiling point of the hydrocarbon polystyrene non-solvent, and agitating for a period of time to allow diffusion of p-cymene from the polystyrene/p-cymene mixture into the hydrocarbon polystyrene non-solvent, continuing to a sufficient extent.

For example, the time may be about 5 minutes to about 10 minutes.

For example, agitating may include stirring with a mechanical stirrer.

For example, greater than about 90 wt% of the p-cymene in a polystyrene/p-cymene mixture can diffuse into the hydrocarbon polystyrene non-solvent, based on the total weight of the polystyrene/p-cymene mixture.

For example, the volume ratio of the first portion of hydrocarbon polystyrene non-solvent to the polystyrene/p-cymene mixture can be from about 2:1 to about 4: 1.

For example, the volume ratio of the first portion of hydrocarbon polystyrene non-solvent to the polystyrene/p-cymene mixture can be about 3: 1.

For example, the precipitated polystyrene may be separated from the first portion of the hydrocarbon waste liquid by a process comprising decanting the first portion of the hydrocarbon waste liquid from the precipitated polystyrene.

For example, the conditions to obtain the washed polystyrene and the second portion of the hydrocarbon waste liquid may comprise adding the second portion of the hydrocarbon polystyrene non-solvent to the precipitated polystyrene at the boiling point of the hydrocarbon polystyrene non-solvent, and agitating for a period of time to allow the p-cymene to diffuse from the precipitated polystyrene to the hydrocarbon polystyrene non-solvent, continuing to a sufficient extent.

For example, the time may be from about 1 minute to about 15 minutes. For example, the time may be about 10 minutes. For example, the time may be from about 2 minutes to about 5 minutes. For example, agitating may include stirring with a mechanical stirrer.

For example, the washed polystyrene can include less than about 0.3 wt% p-cymene. For example, the washed polystyrene can include less than about 0.1 wt% p-cymene.

For example, the volume ratio of the second portion of the hydrocarbon polystyrene non-solvent to the precipitated polystyrene can be about 1:2 to about 2: 1. For example, the volume ratio of the second portion of the hydrocarbon polystyrene non-solvent to the precipitated polystyrene can be about 1: 1.

For example, the washed polystyrene can be separated from the second portion of the hydrocarbon waste stream by a process that includes decanting the second portion of the hydrocarbon waste stream from the washed polystyrene.

For example, the conditions to obtain the second washed polystyrene and the third portion of the hydrocarbon waste liquid may include adding the third portion of the hydrocarbon polystyrene non-solvent to the washed polystyrene at the boiling point of the hydrocarbon polystyrene non-solvent, and agitating for a period of time to allow the p-cymene to diffuse from the washed polystyrene to the hydrocarbon polystyrene non-solvent, continuing to a sufficient extent.

For example, the time may be from about 1 minute to about 10 minutes. For example, the time may be about 5 minutes. For example, agitating may include stirring with a mechanical stirrer.

For example, the twice-washed polystyrene can include less than about 0.1 wt% p-cymene. For example, the twice-washed polystyrene can include less than about 0.05 wt% p-cymene.

For example, the volume ratio of the third portion of hydrocarbon polystyrene non-solvent to the washed polystyrene can be from about 1:2 to about 2: 1. For example, the volume ratio of the third portion of hydrocarbon polystyrene non-solvent to the washed polystyrene can be about 1: 1.

For example, the second washed polystyrene may be separated from the third portion of the hydrocarbon waste liquid by a process comprising decanting the third portion of the hydrocarbon waste liquid from the second washed polystyrene.

For example, after separating the second washed polystyrene from the third portion of the hydrocarbon waste stream, and prior to drying, the processing method may further comprise removing remaining hydrocarbon waste stream by wringing and/or compressing the second washed polystyrene.

For example, at least one of the first portion of the hydrocarbon polystyrene non-solvent, the second portion of the hydrocarbon polystyrene non-solvent, and the third portion of the hydrocarbon polystyrene non-solvent can comprise, consist of, or consist essentially of: a hydrocarbon polystyrene non-solvent having a boiling point of from about 98 ℃ to about 110 ℃ or from about 105 ℃ to about 110 ℃ at a pressure of 1 atm.

For example, the first portion of the hydrocarbon polystyrene non-solvent, the second portion of the hydrocarbon polystyrene non-solvent, and the third portion of the hydrocarbon polystyrene non-solvent can include C₆-C₈Alkanes or petroleum distillates, of C₆-C₈Alkanes or petroleum distillates or consist essentially of C₆-C₈Alkanes or petroleum distillatesAnd (4) composition of an effluent.

For example, a first portion of a hydrocarbon polystyrene non-solvent, a second portion of a hydrocarbon polystyrene non-solvent, and a third portion of a hydrocarbon polystyrene non-solvent can include C₆-C₈Alkane, of formula C₆-C₈Alkanes consisting of or essentially of C₆-C₈And (3) alkane composition.

For example, the first portion of hydrocarbon polystyrene non-solvent, the second portion of hydrocarbon polystyrene non-solvent, and the third portion of hydrocarbon polystyrene non-solvent can comprise, consist of, or consist essentially of petroleum distillate.

For example, the first portion of the hydrocarbon polystyrene non-solvent, the second portion of the hydrocarbon polystyrene non-solvent, and the third portion of the hydrocarbon polystyrene non-solvent can comprise, consist of, or consist essentially of n-heptane.

For example, the first portion of the hydrocarbon polystyrene non-solvent, the second portion of the hydrocarbon polystyrene non-solvent, and the third portion of the hydrocarbon polystyrene non-solvent can all be the same hydrocarbon polystyrene non-solvent.

For example, the first portion of the hydrocarbon polystyrene non-solvent, the second portion of the hydrocarbon polystyrene non-solvent, and the third portion of the hydrocarbon polystyrene non-solvent can all be different hydrocarbon polystyrene non-solvents.

For example, the second portion of the hydrocarbon polystyrene non-solvent and the third portion of the hydrocarbon polystyrene non-solvent can be the same hydrocarbon polystyrene non-solvent, and the first portion of the hydrocarbon polystyrene non-solvent can be a different hydrocarbon polystyrene non-solvent.

For example, the second portion of the hydrocarbon polystyrene non-solvent and the third portion of the hydrocarbon polystyrene non-solvent can comprise, consist of, or consist essentially of n-heptane, and the first portion of the hydrocarbon polystyrene non-solvent can comprise, consist of, or consist essentially of n-hexane.

For example, the conditions to obtain dry polystyrene may include drying the twice-washed polystyrene at a temperature and time to remove residual hydrocarbon polystyrene non-solvent, and continuing to a sufficient extent. For example, the twice-washed polystyrene can be dried at a temperature of about 115 ℃ to about 125 ℃. For example, the twice-washed polystyrene can be dried at a temperature of about 120 ℃.

For example, the conditions to obtain dried polystyrene can include drying the twice-washed polystyrene using an infrared dryer for a period of time to remove remaining hydrocarbon polystyrene non-solvent, continuing to a sufficient extent.

For example, the polystyrene waste may include polar impurities, and the processing method may further include washing the polystyrene waste with a polar organic solvent under conditions to remove the polar impurities.

For example, the polar organic solvent may comprise, consist essentially of, or consist of methanol or ethanol. For example, the polar organic solvent may comprise, consist essentially of, or consist of methanol. For example, the polar organic solvent can comprise, consist essentially of, or consist of ethanol.

For example, the processing method can further include distilling the first portion of the hydrocarbon waste stream, the second portion of the hydrocarbon waste stream, and/or the third portion of the hydrocarbon waste stream under conditions to obtain the para-cymene and/or hydrocarbon polystyrene non-solvent.

For example, the processing method may further comprise recovering p-cymene for the dissolution step.

For example, the processing method can further include recovering the hydrocarbon polystyrene non-solvent for the addition step, the first washing step, and/or the second washing step.

For example, the processing method may further comprise treating the dried polystyrene under conditions to obtain polystyrene particles. For example, the conditions for obtaining polystyrene particles can include extruding dried polystyrene at a temperature of about 140 ℃ to about 160 ℃.

For example, the processing method may further comprise packaging the polystyrene particles. Suitable means for packaging the polystyrene particles may be selected by those skilled in the art.

For example, the processing method may further comprise adding an antioxidant during the dissolving step, the adding step, the first washing step, and/or the second washing step. For example, the processing method may further comprise adding an antioxidant during the dissolving step.

For example, the antioxidant may comprise, consist essentially of, or consist of octadecyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) -propionate.

For example, the antioxidant may be added in an amount of about 0.1 wt% to about 2 wt%, based on the total weight of the polystyrene. For example, the antioxidant may be added in an amount of about 1 wt%, based on the total weight of the polystyrene.

For example, the antioxidant may be added in an amount of about 0.5 wt% to about 2 wt%, based on the total weight of the polystyrene. For example, the antioxidant may be added in an amount of about 1 wt%, based on the total weight of the polystyrene.

For example, the processing method may further comprise adding an additive for reducing or increasing the melt flow index to the polystyrene/p-cymene mixture.

For example, the additive for reducing melt flow index may comprise, consist essentially of, or consist of: lime, talc, silica hydroxide, alumina, aluminum hydroxide, or combinations thereof. For example, the additive for reducing the melt flow index may comprise, consist essentially of, or consist of lime. For example, the additive for reducing the melt flow index may comprise, consist essentially of, or consist of talc.

For example, the additive for increasing the melt flow index may include about 0.0001 wt% to about 1 wt% of a silicone oil. For example, about 0.01 wt% to 0.1 wt% of a silicone oil may be added.

For example, the additive for reducing the melt flow index may be added in an amount of about 0.5 wt% to about 25 wt%, based on the total weight of the polystyrene. For example, the additive for reducing the melt flow index may be added in an amount of about 0.5 wt% to about 5 wt%, based on the total weight of the polystyrene. For example, the additive for decreasing the melt flow index may be added in an amount of about 1 wt% based on the total weight of the polystyrene.

For example, the polystyrene waste may be post-industrial waste, post-consumer waste, or a combination thereof. For example, the polystyrene waste may be post-industrial waste. For example, the polystyrene waste may be post-consumer waste. For example, polystyrene waste may be a combination of post-industrial and post-consumer waste.

For example, the polystyrene waste may comprise, consist essentially of, or consist of expanded polystyrene. For example, the polystyrene waste may comprise, consist essentially of, or consist of white expanded polystyrene. For example, the polystyrene waste may comprise, consist essentially of, or consist of compressed polystyrene.

For example, the processing method may further comprise grinding the polystyrene waste prior to dissolution.

For example, a polystyrene/p-cymene mixture can be obtained at a first location, and the process can further include transporting the polystyrene/p-cymene mixture to a second location where subsequent steps in the process are performed.

For example, polystyrene scrap may include other copolymers. For example, it may comprise butadiene (HIPS), which is a copolymer of Styrene and Acrylonitrile (SAN) or a copolymer of acrylonitrile, butadiene and styrene (ABS).

For example, the waste polystyrene may be a styrene-butadiene copolymer (polystyrene-co-butadiene copolymer).

For example, embodiments of the present disclosure relating to recycled polystyrene may be varied as discussed herein with respect to the processing of recycled polystyrene waste of the present disclosure.

For example, the recycled polystyrene can have a melt flow index of less than about 40g/10 min. For example, the recycled polystyrene can have a melt flow index of about 3 to about 30g/10 min. For example, the recycled polystyrene can have a melt flow index of about 3 to about 25g/10 min. For example, the recycled polystyrene can have a melt flow index of less than about 25g/10 min. For example, the recycled polystyrene can have a melt flow index of about 10 to about 20g/10 min.

For example, the recycled polystyrene can have a melt flow index of less than about 40g/10 min. For example, the recycled polystyrene can have a melt flow index of about 5 to about 30g/10 min. For example, the recycled polystyrene can have a melt flow index of about 5 to about 25g/10 min. For example, the recycled polystyrene can have a melt flow index of less than about 25g/10 min. For example, the recycled polystyrene can have a melt flow index of about 10 to about 20g/10 min.

For example, the recycled polystyrene can have a melt flow index of less than about 30g/10 min. For example, the recycled polystyrene can have a melt flow index of about 3 to about 25g/10 min. For example, the recycled polystyrene can have a melt flow index of about 1 to about 15g/10 min. For example, the recycled polystyrene can have a melt flow index of about 10 to about 15g/10 min. For example, the recycled polystyrene can have a melt flow index of about 5 to about 12g/10 min. For example, the recycled polystyrene can have a melt flow index of about 2 to about 12g/10 min. For example, the recycled polystyrene can have a melt flow index of less than about 15g/10 min. For example, the recycled polystyrene can have a melt flow index of less than about 12g/10 min.

For example, the recycled polystyrene can have an additive content of less than about 5 wt%.

For example, the recycled polystyrene can have an additive content of less than about 3 wt%.

For example, the recycled polystyrene can have an additive content of less than about 2 wt%.

For example, the recycled polystyrene can have an additive content of less than about 1 wt%.

For example, the recycled polystyrene can have an additive content of less than about 0.5 wt%.

For example, the recycled polystyrene can have an additive content of less than about 0.1 wt%.

For example, the recycled polystyrene can have an additive content of less than about 0.05 wt%.

For example, the recycled polystyrene can have an additive content of about 0.05 wt% to about 1 wt%.

For example, the recycled polystyrene can have an additive content of about 0.1 wt% to about 1 wt%.

For example, the recycled polystyrene can have a filler content of less than about 5 wt%.

For example, the recycled polystyrene can have a filler content of less than about 3 wt%.

For example, the recycled polystyrene can have a filler content of less than about 2 wt%.

For example, the recycled polystyrene can have a filler content of less than about 1 wt%.

For example, the recycled polystyrene can have a filler content of less than about 0.5 wt%.

For example, the recycled polystyrene can have a filler content of less than about 0.1 wt%.

For example, the recycled polystyrene can have a filler content of less than about 0.05 wt%.

For example, the recycled polystyrene can have a filler content of about 0.05 wt% to about 1 wt%.

For example, the recycled polystyrene can have a filler content of about 0.1 wt% to about 1 wt%.

For example, the filler may be an inorganic filler.

For example, the recycled polymer may be obtained by involving the recycling of polystyrene waste by treatment with solvents and non-solvents.

The recovered polymer can be obtained, for example, by recovering polystyrene waste by involving a treatment with a solvent, which is p-cymene, and a hydrocarbon polystyrene non-solvent, which is C₆-C₈An alkane, or a mixture thereof.

For example, polystyrene waste may include polystyrene having an average molecular weight of about 200,000 to about 350,000 g/mol.

For example, polystyrene waste may include polystyrene having an average molecular weight of about 230,000 to about 260,000 g/mol.

For example, polystyrene waste may include polystyrene having an average molecular weight of about 260,000 to about 300,000 g/mol.

For example, the recycled polystyrene may be transparent.

For example, the recycled polystyrene may be clear.

For example, the recycled polystyrene can be substantially transparent.

For example, the recycled polystyrene can be at least substantially transparent.

For example, the recycled polystyrene may be obtained by any of the processing methods (processes) and/or methods (methods) described in this disclosure.

There is provided the use of the recycled polystyrene of the present disclosure for preparing a mixture comprising said recycled polystyrene and virgin polystyrene.

Also provided is a method of using the recycled polystyrene of the present disclosure, the method comprising mixing recycled polystyrene with virgin polystyrene.

For example, the mixture can include at least about 10 wt%, at least about 15 wt%, at least about 20 wt%, about 1 wt% to about 50 wt%, about 5 wt% to about 50 wt%, or about 5 wt% to about 30 wt% of the recycled polystyrene.

For example, the recycled polystyrene may include other copolymers. For example, it may comprise butadiene (HIPS), which is a copolymer of Styrene and Acrylonitrile (SAN) or a copolymer of acrylonitrile, butadiene and styrene (ABS).

For example, the recycled polystyrene may be a styrene-butadiene copolymer.

According to another aspect of the present disclosure, there is provided a method for controlling the recycling of polystyrene, comprising:

providing at least one container for storing polystyrene waste to a consumer;

providing instructions to a consumer how to dissolve polystyrene waste in at least one container by using at least one solvent;

optionally monitoring the concentration of polystyrene waste into the at least one solvent, and/or the volume of liquid and/or solid contained in the at least one container;

removing at least a portion of the liquid contents contained in at least one container, the liquid contents comprising polystyrene waste dissolved in at least one solvent;

optionally adding an amount of at least one solvent to at least one vessel;

transporting at least a portion of the liquid contents contained in the at least one container to a facility where polystyrene waste is recovered or processing the polystyrene waste for conversion to recovered polystyrene.

According to another aspect of the present disclosure, there is provided a method for storing polystyrene waste and recycling polystyrene, the method comprising:

dissolving polystyrene waste in at least one container by using at least one solvent;

optionally monitoring the concentration of polystyrene waste into the at least one solvent and/or the volume of liquid and/or solid contained in the at least one container;

optionally adding an amount of at least one solvent to at least one vessel;

transporting at least a portion of the liquid contents contained in the at least one container to a facility where polystyrene waste is recovered or processing the polystyrene waste for conversion of the polystyrene waste to recycled polystyrene.

For example, the recycling of polystyrene or the conversion of polystyrene waste to recycled polystyrene is performed by a method as defined in the present disclosure.

For example, the transportation may be performed by tank truck transportation.

For example, the transportation may be by tank train transportation.

For example, the transport may be by means of a pipeline.

For example, the transport may be via a pipeline.

Examples

Example 1

Recovery of polystyrene waste

In the present study, polystyrene waste was recovered with a process comprising five main steps according to the following sequence:

1. dissolving polystyrene in p-cymene 2. filtering the PS/p-cymene mixture to remove undissolved material

3. Washing with a non-polar solvent which is non-solvent for PS

4. Drying

5. Forming and packaging PS Plastic beads

In the first step (dissolution), polystyrene waste, such as expanded polystyrene after industrial consumption, is dissolved in p-cymene (1-methyl-4- (1-methylethyl) benzene, one of the three possible isomers of cymene, also the only one present in nature). The solubility limit for polystyrene in p-cymene was either 33% (w/w) or 28.5% (v/v) at room temperature, and the density of the polystyrene/p-cymene mixture reached a value of 1.06kg/L, which is higher than the density of pure p-cymene, which was 0.86 kg/L. It was possible to reach the dissolution limit, but the dissolution rate was reduced to 1/3.

During the dissolution step, the polystyrene loses its structural properties and the volume it occupies is reduced. Various non-polar additives including Hexabromocyclododecane (HBCD) and silicone oil for polystyrene manufacture were dissolved in p-cymene solvent. This step is carried out in a closed vented tank called a dissolution module. The purpose of this assembly is to maximize the amount of polystyrene that can be dissolved in a given time. For example, a metal mesh inside the dissolution component may push the expanded polystyrene article into p-cymene, which may, for example, reduce the dissolution time from hours to minutes.

The third step (washing) has the purpose of including: (1) precipitating polystyrene; (2) recovering p-cymene for reuse in step 1; and (3) elimination of different additives that can alter the mechanical properties of the recycled polystyrene.

This step involves first precipitating the dissolved polystyrene with hexane, heptane or any other hydrocarbon with an appropriate boiling point. While heptane was observed to provide the best results in the washing step, other hydrocarbons may also be useful. Hexane and octane were tested in this study. Petroleum distillates having boiling points of about 100 ℃ to about 120 ℃ may also be useful, and may provide, for example, reduced process and/or production costs.

For example, the solvent may have a T about or slightly higher than polystyrene waste_gThe boiling point of (c). Although T of polystyrene_gMay vary, for example, according to molecular weight, but the T of polystyrene waste_gTypically about 98 deg.c. Those skilled in the art will appreciate that for most polystyrenes used in the manufacture of industrial polystyrene articles, T_gTypically only slightly varying with molecular weight or polydispersity. Thus, the solvent may have a boiling point of up to about 110 ℃, for example about 105 ℃ to 110 ℃ at 1atm pressure. Suitable hydrocarbon solvents may, for example, enable more than 90% of p-cymene to migrate into the hydrocarbon solvent and be non-solvent for polystyrene.

To perform the first washing step (i.e., to precipitate the polystyrene), the mixture of dissolved polystyrene in p-cymene was slowly poured into a double-walled stainless steel tank containing the hydrocarbon at its boiling temperature. In an exemplary embodiment, hexane at boiling temperature (69 ℃) is used for this step. In other exemplary embodiments, heptane at boiling temperature (98 ℃) is used for this step. The entire mixture was gently stirred by using a mechanical stirrer. The volume of polystyrene/p-cymene solution added to the hydrocarbon was at a polystyrene/p-cymene solution to hydrocarbon volume ratio of 1: 3. Under these conditions, the polystyrene precipitates as a viscous white paste. The stirring time (about 5 minutes to about 10 minutes) allows a useful amount of p-cymene to diffuse into the hydrocarbon. The solvent mixture supernatant is then removed by simple decantation, possibly followed by a second wash of the precipitated polystyrene.

A second wash was performed in the same tank with heptane. A determined amount of heptane having a boiling temperature of 98 c was introduced into the tank according to a volume ratio of polystyrene to heptane of 1: 1. The entire mixture is boiled under mild mechanical agitation at atmospheric pressure for about 2 minutes to about 5 minutes. The use of a different hydrocarbon in the second wash than in the first wash increases the ductility of the polystyrene, for example, increases the diffusion of residual p-cymene solvent out of the precipitated polystyrene and into the hydrocarbon. Thereafter, the supernatant solvent mixture was removed by simple decantation. The p-cymene remaining in the polystyrene precipitated at this stage was less than 0.1%, calculated on the washing efficiency.

To further reduce the p-cymene present in the polystyrene, a third wash was performed using boiled heptane. The presence of residual solvent can, for example, affect the melt index, also known as Melt Flow Index (MFI). The degree of washing efficiency is inversely proportional to the MFI. The washing conditions used were the same as in the second washing step.

The recovered solvent mixture contains hexane, heptane, p-cymene and/or other hydrocarbon solvents used, as well as non-polar additives extracted from PS. The ratio of p-cymene and additive is higher in the first solvent mixture than in the second and third solvent mixtures. Fractionation was used to separate the different products. P-cymene was used repeatedly in the dissolution step, while hexane and heptane were used repeatedly in the washing step. The recovered additives are considered waste for disposal.

The fourth step (drying) involves drying a polystyrene paste containing about 5 to 37% heptane in a dryer at a temperature of 120 ℃. The objective is to remove substantially all remaining solvent without altering the quality of the polymer.

The fifth step (packaging) involves cutting the dried polystyrene into small particles suitable for distribution of the product to the consumer. The size and shape of the final product is controlled using a pelletizer as is common in the industry.

To limit the degradation of PS, mainly due to oxidation, observed during the drying and extrusion steps, commercial antioxidants such as Irganox can be added in a proportion of about 1%, based on the weight of the polystyrene^TM1076 (octadecyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) -propionate). The compound is acceptable for food applications, has a melting point of 50 ℃, and can be added at various times in the process: i.e. together with p-cymene, in a washing step and/or a final extrusion step.

Table 1 shows the results of recycling various types of waste polystyrene using the steps of the process described above^[1]。

TABLE 1^[1]

^[1]All experiments were performed using three washes of heptane with heptane to PS/cymene mixtures in volume ratios of 3:1, 1:1 and 1:1, using extraction times of 15 min, 10min and 5 min, respectively.

^[2]The mixture used in all experiments also included p-cymene to make a total of 100 wt%.

^[3]ASTM D1238 standard was used for each result.

^[4]In a furnace at 120 ℃ an aluminum plate with a diameter of 8cm was used. Unless otherwise specified, to<The polystyrene is dried to a thickness of 5 mm.

^[5]The regrind beads come from a tray and already have a lower melt flow index. The quality of the polystyrene being reduced by the mixture due to the high molecular weightMelt flow index.

^[6]Lime and talc were added to the PS cymene mixture prior to washing.

Irganox 1076 has the property of protecting against oxidation. Many of the results show a helpful effect on the color of the product. The addition of butadiene to styrene results in the formation of styrene-butadiene copolymers, which exhibit better impact resistance than pure polystyrene. The butadiene units in the styrene-butadiene copolymer can be used to build up a three-dimensional matrix with polymer chains. By establishing the linkage between the polymer chains, the molecular weight increases and the melt flow index must then decrease. The styrene-butadiene copolymer polymer contained 4% butadiene. A small amount of butadiene must be sufficient to see the difference in melt flow index, but the results are uncertain.

As can be seen in table 1, the experiment shows better results when the polystyrene-cymene mixture has a lower concentration. Dilution of the mixture in a non-solvent improves diffusion and therefore solvent extraction. The addition of solid particles to polymer blends is a common practice in the polystyrene industry to reduce cost or improve mechanical properties.

Table 2 shows the results of including the antioxidant Irganox 1076 in the different steps of the process.

TABLE 2

^[1]For each result, the ASTM D1238 standard was used.

As can be seen in table 2, the product color was white for all samples. The MFI of the product resulting from the process of adding Irganox 1076 to the polystyrene/p-cymene mixture was minimal.

Table 3 shows the effect of the change in mechanical conditioning (mechanical conditioning) and drying steps. There was about a 37.5% difference between the washed polystyrene and the dried polystyrene. At this point, all heptane had evaporated. Moreover, it is possible to remove 14% of the heptane from the washed polystyrene using only the extrusion and granulation steps. Heptane was recovered in the process to repeat the washing process. The source of polystyrene did not have any significant effect in the drying step of these studies.

TABLE 3^[1]

^[1]All drying was carried out in an oven at 120 ℃.

^[2]All mixtures tested also included p-cymene to make a total of 100 wt%.

^[3]The values are provided as wt% based on the total mass before granulation.

Example 2

Further testing was conducted to prepare recycled polystyrene. Such tests were performed by using a method similar to that previously described in example 1, but without the addition of any Irganox. These tests were carried out on a laboratory scale on true white expanded polystyrene for packaging.

Thus, the results of such testing are provided below

DSC(ASTM D3418)：T_g＝108.1℃

IZOD impact test (ASTM D4812): the average impact of 4 tests is 13,78KJ/m²175,72J/m, energy 0,55J with total fracture

Table 4: MFI test MFI (ASTM D1238 for Dynisco D4002 at 200 ℃):

testing	MFI(g/10min)
		1	11.44
2	11.01
		3	10.70
Average	11.05

Ash content (ASTM D5630): 0.10

TABLE 5 VICAT test

VICAT softening temperature (ASTM D1525):

TABLE 6 VICAT test

Traction test (ASTM D638)

Example 3

Further tests were conducted to prepare recycled polystyrene. Such tests were performed by using a method similar to that described previously in example 1. The process is carried out continuously, scaling up bringing the process from the laboratory level to the industrial level. For example, the process allows about 10kg of recycled polystyrene to be prepared per hour. It is to be noted that the limiting factor in this case with respect to the productivity of the process does not exist in the process itself, but in some type of plant for carrying out the process. By having some equipment that allows for accepting larger volumes or quantities, the overall process can easily reach about 500 to about 1000kg of recycled polystyrene per hour.

Thus, the results of such testing are provided below.

According to ASTM D1238-13, MFI 22g/10 min.

Reference has been made in detail to the specific embodiments, but it will be understood that many modifications thereof will be apparent to those skilled in the art. The foregoing description and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Claims

1. The combined use of p-cymene and a non-solvent having a boiling point of 98 ℃ to 110 ℃ at a pressure of 1atm for the recovery of polystyrene.

2. Use according to claim 1, wherein the p-cymene is used to dissolve polystyrene and the non-solvent is used to precipitate polystyrene as a paste.

3. Use according to claim 2, wherein the precipitation of polystyrene is carried out at the boiling point of the non-solvent.

4. Use according to any one of claims 1-3, wherein the non-solvent is heptane.

5. Use according to any one of claims 1 to 4, wherein styrene is precipitated from a mixture comprising p-cymene, heptane and polystyrene, and the precipitation is carried out at a temperature of about 98 ℃.

6. A composition for the production of recycled polystyrene, characterized in that it comprises polystyrene, p-cymene and a non-solvent having a boiling point between 98 ℃ and 110 ℃ at a pressure of 1 atm.

7. The composition of claim 6, wherein the non-solvent is heptane.